<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div id="app">
    <p>{{getResult}}</p>
    <p>{{getResult}}</p>
    <p>{{getResult}}</p>
    <p>{{getSum()}}</p>
    <p>{{getSum()}}</p>
    <p>{{getSum()}}</p>
  </div>
</body>
<script src="../lib/vue.js"></script>
<script>
  let app = new Vue({
    el: "#app",
    data: {
      arr: [1,2,3,4]
    },
    methods:{
      getSum(){
        console.log("开始计算");
        let arr = this.arr;
        let sum = 0;
        for(let i = 0; i < arr.length; i++){
          sum += arr[i];
        }
        return sum;
      }
    },
    computed: {
      getResult(){
        console.log("开始计算");
        let arr = this.arr;
        let sum = 0;
        for(let i = 0; i < arr.length; i++){
          sum += arr[i];
        }
        return sum;
      }
    }
  })
</script>
</html>